Clutch and brake for sewing machines



June 8, 1954 Filed May '7, 1948 A. M. scHwEDA CLUTCH AND BRAKE FOR SEWING MACHINES 3 Sheets-Sheet l INVENTOR. ALBERT M SCHWEDA ATTORNEYS June 8, 1954 A. M. SCHWEDA CLUTCH AND BRAKE FOR SEWING MACHINES 3 Sheets-Sheet 2 Filed May 7, 1948 JNIEN TOR. ALBERT M. SCHWEDA ATTORNEYS June 8, 1954 Filed May 7, 1948 3 Sheds-Sheet s IlHIHHI IH. 8

O E N 1' m I u I 9 9 v I I l f 'IHI ln.

LO 2 g INVENTOR.

ALBERT M. SCHWEDA ATTORNEYS Patented June 8, 1954 CLUTCH AND BRAKE FOR SEWING MACHINES Albert M. Schweda, Chicago, 111., assignor to Union Special Machine Company, Chicago, Ill., a corporation of Illinois Application May 7, 1948, Serial No. 25,605

2 Claims.

This invention relates to an improved power unit comprising an electric motor and aclutch, particularly adapted for use in driving a sewing machine.

Power units of the type to which the invention is directed are customarily provided with constant speed motors. A clutch associated with themotor serves to couple the latter with a driven pulley, which, in turn, is connected by a belt with a pulley on the machine to be driven. Formerly, belts of circular cross-section were frequently used and these were able to slip readily in relation to one of the connected pulleys, so that the operation of the driven machine could .be easily retarded. However, in recent years the practice has been to use a V-belt cooperating with V-shaped grooves in the pulleys to transmit the torque more positively. To retard the operation of a sewing machine driven by such a belt, it has been necessary to cause slippage between the clutch elements rather than between the belt and pulleys. Skillful operation-of the foot treadle, or other control means for the clutch, has been required to insure a sufiicientiy light engagement of the clutch to permit it to be slipped.

There are various circumstances-under which it is desirable to retard the speed of operationof an industrial sewing machine. For example, in machines of the type used for the seaming of hosiery, such a light thread isemployed that if the machine is started up suddenly the needle thread is likely to snap, Therefore, it is desirable to commence a hosiery seaming operation slowly and .then to get up to full speed quicklyafter the ma- .chine has been set in operation. Also in hemming operations, operators have found it desirable to commence the stitching slowly, until the hem is properly started, and then to operate the machine at full speed. In the stitching of collars, it is necessary to sew up to an exact point. To accomplish this, with machines driven by prior power units, operators have usuallystopped the sewing machine before the end of the seam is reached and they have then attempted to slip the clutch so that the machine will sew slowly in completing the seam. Some sewing operations require such care in the formation of the entire seam that it has been found desirable to operate the machine at a reduced speed throughout.

A primary object of the invention has been to provide a power unit which may be readily and easily controlled by the operator of alsewing machine to transmit to the latter, at will, either the .full driving. effort of the motor or a reduced torque.

Another object has been to provide a unit of the foregoing character with a single control member, such as a treadle, which may be readily operated to select the amount of torque to be transmitted. The preferred arrangement is such that upon a predetermined operation of the treadle, which need not be particuiarly exact, a relatively low torque is transmitted, whereas upon full operation of the trcadle a substantially greater torque is transmitted.

A further object of the invention has been to provide a unit of the character indicated which will transmit either .a relatively small or a relatively great torque from a constant power and constant speed motor selectively, at will, upon the full operation of a clutch controlling member by the operator,

Toward the foregoing ends, the illustrative formof the invention involves the provision of a dual friction clutch connection between the motor and the driven pulley. The arrangement is such that initial operation of the clutch engaging member serves to bring together only certain friction faces which are of relatively small radius while upon full operation of the clutch engaging member, other friction faces, of greater radius, are made effective so that a substantially greater torque is transmitted. Moreover, the arrangement is such that upon the limited or preliminary operation of the clutch engaging member only a relatively small force is effective to urge the friction surfaces together, whereas full operation of the clutch engaging member provides a much greater force to urge the friction faces together.

Thus, the magnitude of the torque transmitted is increased, upon fulloperation of the clutch en gaging member, both by virtue of the greater radius of the friction surfaces and the greater pressure creating the friction.

A feature of this phase of the invention has been theprovision of readily replaceable friction faces or elements on certain of the clutch members so that effective friction may be maintained at all times. This is of particular importance in relation to at least one of the clutch surfaces which are rendered effective upon the preliminary operation of the clutch engaging member, since these surfaces are subject tosubstantial wear due to slippage.

Another special feature of a preferredform of the invention, identified with the foregoing objects, is the provision of means by which the action of the clutch may be restricted, at the will of the operator, to the engagement of only the friction surfaces of small radius, regardless of the force applied by the operator to the foot treadle or other controlling means. This is of special utility when the sewing machine driven by the unit is used, during a particular period, for sewing operations which must be continuously carried out at less than the full speed of the machine.

A further feature is the provision, in combination with the dual clutch, of a brake which will quickly arrest the operation of the driven parts upon release of the clutch engaging member. This enables abrupt stopping of the sewing machine after a seam has been completed at a reduced speed.

Another object of the invention has been to provide means for quickly and readily adjusting the position of the driven pulley of a power unit for belt tightening purposes and the like. The means provided in connection with this phase of the invention is such that the tension on the belt may be increased or reduced by the simple depression of a knob and the manual shifting of the unit to the position desired. Upon release of the button the unit is retained in the position to which it has been shifted. Replacement of the belt is also greatly facilitated by the provision of this means.

Other objects, features, and advantages of the invention will be apparent from the detailed description of an illustrative form of the same which will now be given in conjunction with the accompanying drawings, in which:

Fig. l is a vertical sectional view taken along the axis of a power unit embodying the invention;

Fig. 2 is an end elevational view of the unit, with parts broken away for better illustration of concealed parts;

Fig. 3 is a detail view in section along the line 3-3 of Fig. 4;

Fig. 4 is a detail view in section along the line :34 of Fig. 2;

Fig. 5 is a front elevational view of the upper portion of the unit;

Fig. 6 is a face view of a friction element embodied in the unit; and

Fig. '7 is a side view of said friction element.

Referring now to the drawings, the illustrative unit comp 'ises a supporting or carrying member [0 having a fiat horizontally extending portion I 1 adapted to be secured by screws or the like to the under surface of a table on which the sewing machine to be driven may be mounted. A main motor housing !2 is adapted to be pivotally and adjustably secured to the supporting member [0. For this purpose the housing I2 is formed with upwardly and rearwardly extending ears 3 positioned at opposite sides of the member iii and adapted to receive a pivot pin M which passes through an aperture in a downwardly extending portion of the member l0. At the forward end of the horizontally extending portion I I of the supporting member there is swivelly mounted a downwardly extending bar I5. This is swivelly mounted on the bracket by a pin it and is preferably in the form of a circular rack bar. Said rack bar is slidably received by a block i! having a laterally extending trunnion l8 rotatably received by an upwardly and forwardly extending ear I?! integral with the motor housing l2. Within the block ii there is mounted a spring pressed plunger 2e having an enlarged head 2! at its upper end, this plunger being urged upwardly by a spring 22 acting against the underside of the head 2! and against the bottom wall of a 1 recess 23 formed in the block. At the lower end of the plunger 26 there is secured, integrally or in any other suitable way, a laterally extending tooth 24 adapted to cooperate with any one of the spaces between a series of teeth 25 in the under surface of the rack bar. It will be seen that when the plunger 29 is depressed, by manual engagement of the cap 2!, the tooth 25 is disengaged from the rack teeth so that the block I"! may be shifted to any selected position along the bar l5. Upon release of the h ad or button 2! the spring 22 will engage the tooth 24 with the rack bar at the selected position. If it is desired to replace the belt (not shown), which will be hereinafter referred to, the button 2! may be depressed and the motor housing lifted, thereby causing the block if to slide freely upward along rack bar l5 until suiiicient slack has been provided to enable removal of the belt from the pulley. The unit may be locked in this position by release of the button 2! until the belt has been replaced. To limit the downward movement of the unit a screw 26, having an enlarged head, may be provided at the lower end of the rack bar i5. The head of this screw will serve to arrest the downward movement of the block ll along the rack bar.

The electric motor forming a part of the improved unit may be of any suitable character. It may, for example, be a three-phase four pole motor. In the illustrative form of the invention the housing i2 is provided with an inwardly extending sleeve or hub 23'! in which is journalled a shaft The latter may suitably be mounted in ball bearings 29 and 36 positioned in enlarged recesses at the outer and inner ends of the hub 2?. A flywheel 3| secured to the inner reduced end of the shaft 28 provides a shoulder adapted to bear against the inner raceway of the bearing 30. The several parts mentioned are retained in assembled relation on the housing by means of a washer 32 and nuts 33 cooperating with a screw-threaded extension of the shaft 28. These serve to lock the inner raceway of the bearing 29 against a shoulder on the shaft.

The motor comprises an inner stationary electromagnetic member carried by the outer surface of the hub 21. This stationary member includes a suitable winding fi l and pole pieces 35. The latter may be secured to the housing by means of long screws 36 cooperating at their inner ends with threaded ferrules 37 passing through the laminated pole pieces. Surrounding the pole pieces 35 is a rotor member 38, this being carried by a ring 39 secured by a series of screws 20 to the flywheel 3!. Suitable connections are provided for supplying current to the windings of the motor for driving the same. A socket 4! may be mounted on the motor housing for delivery of the current to the motor.

To the outer face of the flywheel 3| is secured, by means of screws a friction ring 43 adapted to form one part of a clutch. At the center of the flywheel a second friction ring 34 is provided, this being mounted by rivets 45 or the like upon a disc carried at the end of a stud 57. The latter is received with a snug sliding fit within a bore 58 provided in the inner end of the shaft 28. A spring 39 seated within the bore 18 serves to urge the stud t? and disc 16 outwardly toward the right in Fig. 1. To prevent rotation of the disc is and to guide it in its axial movements, a pair of studs 58 is provided, these being disposed at some distance from the axis of the disc and hav- .a slidable sleeve ing a snug sliding fit within passages extending through the flywheel. Screws 52, having enlarged heads and having their shanks threaded into the studs Elli, serve to limit the movement of the disc toward the right, Fig. l, in response to the action of the spring 48. By turning the screws 52, the extent of movement of the disc toward the right may be adjusted within suitable limits. In the normal position of the parts, as shown in outer face of ring 43.

A detachable cover member 53 is provided at the right end (Fig. 1) of the motor housing, this being secured to the housing by any suitable means, such as screws 54. An outwardly projecting portion 55 of the cover provides a bearing for 55 which is recessed at its two ends to receive ball-bearing unit iii and 58. The inner raceways of these bearing units are carried by a shaft 59 which is thus journalled within the sleeve. Secured to the inner end of the shaft 59 is a clutch element til having a surface 61 opposite the ring 3 for frictional engagement therewith. Toward the center of the element 552 an annular surface d2 is provided for cooperation with the friction ring t l. Extending transversely of the projection and suitably journalled therein is a rock. shaft having secured to its outer end an operating arm 64, the latter being adapted for connection with a treadle, or other suitable means operable at will by the operator, to cause engagement of the clutch. A pinion 65 at the inner end of the shaft 63 cooperates with a rack segment 86 carried by the sleeve 56 and serves to impart sliding movements to the latter in response to rocking of the shaft 53. Rack segment 66 travels in a key slot 62* in the projection 55 and serves the additional function of preventing rotation of the sleeve 5%. The outer end of the shaft 59 is splined and adapted to receive a pulley 68 which is secured to the shaft by nuts 69. These nuts serve to hold the shaft, the bearings, the clutch element 68, and the pulley in assembled relation to the sleeve 56.

The arrangement of the foregoing parts is such thata counterclockwise rocking of the arm 64 and shaft 63 will cause the sleeve 56 to be shifted to- Ward the left (Fig. 1) carrying with it the driven clutch element 68. Upon slight movement toward the left, the surface 52 will be brought into engagement with the outer face of the ring 44 and thus establish a driving connection between the motor and the shaft 59. Upon further movement of the sleeve 5% toward the left, the disc 46 will be forced into the flywheel, thus compressing the spring 49 and increasing slightly the pressure acting between the ring as and surface 52. After a slight inward movement of the disc 46, the surface El on the driven clutch element will be engaged with the outer face of the ring 43 so that a substantially greater frictional torque will be imparted to the driven clutch element. In this connection it should be noted that the pressure exerted between the surface 6! and the outer face of ring 43 may be considerable, since this is dependent upon the force applied by the operator to the outer end of the arm 64. This force may be substantially greater than that created by the spring 49 which is the only force serving to urge the ring 44 against the surface Bl It will be apparent that when the torque is transmitted to the element as merely through the ring 44, relative slippage of the clutch surfaces may be rather readily brought about. This is due not only to the relatively small radius of the surfaces which are frictionally engaged but also to the limited pressure created by the spring 49. To facilitate slippage further the ring 44 may, if desired, be formed of a material having a lower coefficient of friction in relation to the element 69 than does the ring :23. The latter may, for example, be formed of cork, while the ring 14 may be formed of some harder material, such as a resin impregnated fabric or the like.

If desired, provision may be made for limiting the sliding movement of the sleeve 5% so that the surface 6! will not be brought into engagement with the ring :13, regardless of the force supplied by the operator to the treadle connected with the arm M. For this purpose a definite stop may be provided'for limiting the permitted movement of the sleeve 55 toward the left. This stop is preferably made readily and quickly adjustable by the operator to render it effective or ineffective at will. It may, for example, be in the form of a ring It adjustably mounted upon an extension ll of the sleeve 56, by screw threaded engagement therewith. The periphery of ring is may be knurled to facilitate its rotation and adjustment by the operator. Whenever it is desired to limit the movement of the sleeve 55 toward the left (Fig. 1), the ring may be turned until it is so close to the outer end of the projection 55 that it will engage the latter before the surface 6| engages the ring 43. It should, however, be spaced sufiiciently from projection 55 to permit engagement of surface 62 with ring 44 and slight inward movement of the latter. The periph ry of ring "it may be provided with a mark to indicate when it is properly positioned for this purpose. This arrangement is desirable when the machine is to be used in performing stitching operations which require continuous slippage of the clutch elements, in order to slow down the speed of operation of the driven sewing machine. When higher speed operation is desired, either continuously or intermittently, the ring is may be backed away from the end of the projection 55 to render the dual clutch construction operative.

On the upper surface of the projection 55, which may be suitably flattened, a slide "52 is adjustably mounted. It may be locked in desired position by means of a screw it threaded into the projection 55 and cooperating with an elongated slot in the slid '12. When the screw 13 is loosened, the position of the slide 72 may be adjusted by turning a screw M which is threaded into the end of the slide and has a collar held against axial movement by a groove in projection 55. After the new adjustment has been effected, the screw 13 is retightened. Slide 12 carries at its inner end a brake element 15 arranged to cooperate with the outer face of the clutch element 6c. The latter is shifted into engagement with the brake element whenever the operator releases the treadle and permits the arm 54 to be rocked clockwise by the spring 8464. Thus, when a seam has been completed and the clutch is disengaged, the driven element so and the pulley 53 will be brought to a quick stop by the brake.

The pivot pin i i, as shown in Fig. 1, extends a substantial distance outwardly from the plate 53 and serves to support a swingable belt guard 16 which may suitably be of the form disclosed in the pending application of Albert C. Peterson, Serial No. 4,087, filed January 24, 1948, now Patent No. 2,481,867. A spring 77, having one end engaged in an aperture in the plate 53 and having its other" end engaged with the rear surface of the belt guard, serves to hold the latter normally in its active position. The guard may be readily swung into an inactive position, against the action of the spring, whenever access to the pulley E8 is required.

It will be seen from the foregoing that a double acting clutch has been provided which, at the will of the operator, will transmit ither a relatively small or a relatively great torque from the motor to the driven element 60. When the clutch engaging means is so operated as to engage only the ring 14 with surface 62, slippage of the clutch may be readily brought about so that the driven machine may be operated at a reduced speed. The transmitted torque will be substantially greater when the surface 6! is also engaged with the ring 43 so that slippage is substantially prevented. When the unit is employed to drive a sewing machine, the arrangement permits slow starting and stopping of the machine with high speed operation in between. As the arm 55 is rocked downwardly in normal use of the unit, slippage will occur between the ring 44 and surface 62 for an instant before the clutch is fully engaged. This allows the sewing machine to pick up speed gradually and overcomes the danger of thread breakage which often occurs when relatively fine threads are employed, as in hosiery seaming. Operation of the machine at desired speeds for other special operations is also permitted, as explained above. Means, operable quickly and simply, is also provided for varying the tension of the driven belt to insure proper delivery of the desired torque to the driven machine.

While an illustrative embodiment of the invention has been described in considerable detail and certain advantages of it have been pointed out, it will be understood that various changes may be made in the construction and arrangement of the several parts and that various other uses, than those specified, may be made of the invention.

What I claim is:

l. A power unit for sewing machines which comprises an electric motor having a housing and a rotary member, a driven member axially alined with said rotary member, a sets of flat friction surfaces on said members disposed in planes transverse to the axis of said member and at different radial distances from the axis thereof, said friction surfaces on one of said members being substantially coplanar, spring means for urging said members apart so that said friction surfaces are normally disengaged, the friction surfaces of one of said sets being normally spaced a greater distance apart than those of another, braking means rendered effective by said spring means for arresting rotation of said driving member and arranged to limit the relative movement of said members by said spring means, means operable at will for positively shifting one of said members axially toward the other to disable said braking means and to cause engagement of one of said sets of surfaces or a plurality thereof as desired, and means adjustable by the operator for positively limiting the shifting of said one of said members to prevent engagement of one of said sets of flat friction surfaces while enabling engagement of the other of sets of fiat friction surfaces, said adjustable means comprising a ring having screw threaded engagement with one of said members and arranged to cooperate with said housing.

2. A power unit for sewing machines as set forth in claim 1 in which the friction surfaces of said one of said sets is at a greater radial distance from the axis of said members and has a greater coefiicient of friction than those of said other of said sets friction surfaces.

plurality of References Cited in the file of this patent UNITED STATES PATENTS Peterson 1- Sept. 

